Nat Sci 179 Lecture Notes Ch. 28—Female Reproductive System

Front 1

oogenesis

Back 1

egg production

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early oogonia

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(precursors of ova) develop before birth

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remain in early meiosis I until adolescence

Back 3

-then FSH stimulates them to go to metaphase II of meiosis
-meiosis is not completed unless it is fertilized
-meiosis produces one oocyte and 3 polar bodies

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by puberty about 400,000 ova are present

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-if she ovulates once a month from age 14-50, this is 480 times
-it is not true that menopause occurs because she “runs out” of ova

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Sexual Cycle

Back 5

reproductive cycle

sexual cycle

ovarian cycle

menstrual cycle

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reproductive cycle

Back 6

events from fertilization to giving birth

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sexual cycle

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-events that occur monthly when pregnancy does not occur
-includes two cycles;

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ovarian cycle

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(events in the ovaries)

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menstrual cycle

Back 9

(corresponding changes in uterus)

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hierarchy of control in sexual cycles

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hypothalamus  pituitary  ovaries  uterus
-there is also feedback from the ovaries to the hypothalamus & pit.

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Ovarian Cycle

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1) follicular phase

-menstrual phase
-preovulatory phase

2) ovulation

3) postovulatory phase

-luteal phase
-premenstrual phase

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menstrual phase

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-days 1-5
-from start to stop of menstrual fluid being discharged
-several follicles develop
-follicle = ovum and surrounding cells and space
-FSH is high

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preovulatory phase

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-day 6-14
-from end of menstruation to day of ovulation
-continued development of one follicle (others degenerate)
-FSH drops
-continuation of meiosis until stopping at metaphase II
-in the uterus, endometrial tissue lining uterus is building
-sharp rise in LH and estrogen at day 13

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ovulation

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-day 14
-oocyte is released from follicle
-oocyte is swept into uterine tube by cilia
-may fall into pelvic cavity and die or be fertilized  ectopic pregnancy

Postovulatory phase

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luteal phase

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-day 15-28
-corpus luteum forms from the empty follicle
-stimulated by LH (hence the name)
-secretes an androgen which is converted to progesterone

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luteal phase - 2

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-in uterus, mucus & glycogen are secreted, causing endometrium to thicken
-eventually, corpus luteum atrophies
-causes progesterone to drop, and menstruation will occur
-if pregnancy occurs, the corpus luteum will remain for about 3 months

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premenstrual phase day 27-28

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-endometrial tissue dies, mixes with blood
-leaves body as menstrual fluid

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in pregnancy:
-in weeks 7-12

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corpus luteum maintains hormones needed

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from weeks 7-17

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corpuse luteum degenerates & placenta takes over making needed hormones
-includes high amounts of estrogens and progesterone

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hCG (human chorionic gonadotropin)

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-hormone secreted by embryo & placenta
-presence in urine is basis of at-home pregnancy tests
-detected as early as 8-9 days after implantation

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ovum must be fertilized in distal half of uterine tube

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an unfertilized egg would not live long enough to reach the uterus

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“products of conception”

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refers to blastocyst (or embryo or fetus, depending on stage of development) plus placenta, membranes.

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-terms used in development

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-zygote: fertilized egg
-blastocyst: first 2 weeks
-embryo: weeks 2-8

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fetus

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weeks 9 to birth